Thermal energy recovery device

ABSTRACT

Provided is a thermal energy recovery device in which poor lubrication of a bearing can be inhibited when an expander is driven. The thermal energy recovery device includes an evaporator ( 10 ), an expander ( 20 ), a power recovery machine ( 30 ), a condenser ( 40 ), a pump ( 50 ), a circulation flow path ( 60 ), a cooling flow path ( 70 ) for supplying working fluid from the pump ( 50 ) partially to the power recovery machine ( 30 ), an on-off valve (V 1 ) provided in the cooling flow path ( 70 ), and a control unit ( 80 ), in which the expander ( 20 ) has a rotor ( 21 ), a bearing ( 22 ), and a primary casing ( 23 ), and in which the power recovery machine ( 30 ) has a power recovery unit ( 31 ) and a secondary casing ( 35 ), and in which upon reception of a stop signal for stopping power recovery by the power recovery machine ( 30 ), the control unit ( 80 ) closes the on-off valve (V 1 ).

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a thermal energy recovery device.

Description of the Related Art

There have conventionally been known thermal energy recovery devices forrecovering power from exhaust heat from various types of equipment suchas plants. For example, JP 2012-97725 discloses a generator system(thermal energy recovery device) including an evaporator, a closedgenerator, a condenser, a fluid supply pump, a circulation flow pathconnecting the evaporator, the closed generator, the condenser, and thefluid supply pump in this order, and a cooling tube. The evaporatorevaporates working medium. The closed generator generates electric powerfrom the expansion energy of working medium flowing out of theevaporator. Specifically, the closed generator has a screw turbine forexpanding working medium, a generator connected to the screw turbine viaan output shaft, and a housing case housing the screw turbine, theoutput shaft, and the generator therein. The condenser condenses workingmedium flowing out of the closed generator. The fluid supply pumpdelivers working medium flowing out of the condenser to the evaporator.The cooling tube connects a site downstream the fluid supply pump in thecirculation flow path and the housing case such that working medium ofliquid phase discharged from the fluid supply pump is partially suppliedinto the housing case.

In the thermal energy recovery device, since working medium of liquidphase discharged from the fluid supply pump during operation ispartially supplied into the housing case through the cooling tube, thegenerator is cooled effectively during operation of the device.

Such a thermal energy recovery device as described in JP 2012-97725 hasa concern that the lubrication of the bearing of the screw turbine maybe insufficient when the device restarts after stopping. Specifically,when the thermal energy recovery device comes into a stop operation, therotational speed of the pump starts decreasing. In this state, ifworking medium of liquid phase continues to be supplied into theexpander through the cooling tube, working medium of liquid phase thathas existed in the evaporator and heated by heating medium to beevaporated and then flowing into the expander, for example, may becooled and thereby condensed by the working medium of liquid phasesupplied through the cooling tube to be reserved within the expander.When the accumulation of the working medium of liquid phase then causesthe bearing of the screw turbine to be immersed in the working medium ofliquid phase, there is a concern of poor lubrication of the bearing whenthe device restarts (when the screw turbine is driven).

It is hence an object of the present invention to provide a thermalenergy recovery device in which poor lubrication of a bearing can beinhibited when an expander is driven.

In order to achieve the foregoing object, the present invention providesa thermal energy recovery device including an evaporator for evaporatingworking medium through heat exchange between heating medium and theworking medium, an expander for expanding working medium flowing out ofthe evaporator, a power recovery machine connected to the expander, acondenser for condensing working medium flowing out of the expander, apump for delivering working medium flowing out of the condenser to theevaporator, a circulation flow path connecting the evaporator, theexpander, the condenser, and the pump in this order, a cooling flow pathfor supplying working medium of liquid phase flowing out of the pumppartially to the power recovery machine, an on-off valve provided in thecooling flow path, and a control unit, in which the expander has a rotorto be rotationally driven by the expansion energy of the working medium,a bearing that bears the rotor such that the rotor is rotatable, and aprimary casing housing the rotor and the bearing therein, and in whichthe power recovery machine has a power recovery unit connected to therotor to rotate together with the rotor and thereby recover power and asecondary casing housing the power recovery unit therein and having ashape in communication with the interior of the primary casing, and inwhich upon reception of a stop signal for stopping power recovery by thepower recovery machine, the control unit closes the on-off valve.

In the thermal energy recovery device, upon reception of a stop signalfor stopping power recovery by the power recovery machine (when thepower recovery unit is not required to be cooled), the control unitcloses the on-off valve that is provided in the cooling flow path,whereby working medium of liquid phase is inhibited from beingaccumulated within the secondary casing and the primary casing.Accordingly, the bearing of the expander is inhibited from beingimmersed in the working medium of liquid phase and thereby poorlubrication of the bearing is inhibited when the thermal energy recoverydevice restarts.

In the case above, the secondary casing may have an introducing portionconnectable to the cooling flow path and capable of introducing workingmedium of liquid phase supplied through the cooling flow path into thesecondary casing.

In the aspect above, the power recovery unit is cooled effectively bythe working medium of liquid phase supplied through the cooling flowpath into the secondary casing.

Alternatively, the power recovery machine may further have a jacketprovided in the secondary casing to form a cooling space that allowsworking medium of liquid phase to flow between the jacket and thesecondary casing, in which the jacket has an introducing portionconnectable to the cooling flow path and capable of introducing workingmedium of liquid phase supplied through the cooling flow path into thecooling space.

In the aspect above, the power recovery unit is cooled effectively viathe secondary casing by the working medium of liquid phase suppliedthrough the cooling flow path into the cooling space.

The present invention also provides a thermal energy recovery deviceincluding an evaporator for evaporating working medium through heatexchange between heating medium and the working medium, an expander forexpanding working medium flowing out of the evaporator, a power recoverymachine connected to the expander, a condenser for condensing workingmedium flowing out of the expander, a pump for delivering working mediumflowing out of the condenser to the evaporator, a circulation flow pathconnecting the evaporator, the expander, the condenser, and the pump inthis order, a cooling flow path for supplying cooling medium differentfrom the working medium to the power recovery machine to cool the powerrecovery machine, an on-off valve provided in the cooling flow path, anda control unit, in which the expander has a rotor to be rotationallydriven by the expansion energy of the working medium, a bearing thatbears the rotor such that the rotor is rotatable, and a primary casinghousing the rotor and the bearing therein, and in which the powerrecovery machine has a power recovery unit connected to the rotor torotate together with the rotor and thereby recover power and a secondarycasing housing the power recovery unit therein and having a shape incommunication with the interior of the primary casing, and in which uponreception of a stop signal for stopping power recovery by the powerrecovery machine, the control unit closes the on-off valve.

Also in the thermal energy recovery device above, poor lubrication ofthe bearing of the expander is inhibited when the device is driven(starts to operate).

The thermal energy recovery device preferably further includes a liquiddraining flow path for returning working medium of liquid phase withinthe primary casing or the secondary casing to the downstream side of theexpander and the upstream side of the pump.

With the arrangement above, since the working medium of liquid phasewithin the primary casing or the secondary casing is dischargedeffectively from the primary casing or the secondary casing through theliquid draining flow path, the bearing is more reliably inhibited frombeing immersed in the working medium of liquid phase.

In the case above, the thermal energy recovery device preferably furtherincludes a liquid draining valve provided in the liquid draining flowpath, a bypass flow path for bypassing the expander, a bypass valveprovided in the bypass flow path, and a shutoff valve provided at a siteof the circulation flow path between a portion where the circulationflow path and an upstream end portion of the bypass flow path areconnected and the expander, in which upon reception of a stop signal forstopping power recovery by the power recovery machine, the control unitreduces the rotational speed of the pump, closes the shutoff valve andopens the bypass valve, and closes the on-off valve and, after the pumpis stopped, opens the liquid draining valve.

With the arrangement above, the working medium of liquid phase withinthe primary casing or the secondary casing is discharged effectivelyfrom the casing and, in addition thereto, the working medium isinhibited from flowing into the primary casing until the pump isstopped. Specifically, if the liquid draining valve were opened beforethe pump is stopped, the working medium discharged from the pump to flowthrough the bypass flow path to the downstream side of the expandermight counterflow from the downstream side of the expander through thecirculation flow path to flow into the primary casing of the expander tobe liquefied within the primary casing. In contrast, in the thermalenergy recovery device, since the control unit is arranged to open theliquid draining valve after the pump is stopped, such a trouble asdescribed above is inhibited.

As described heretofore, in accordance with the present invention, it ispossible to provide such a thermal energy recovery device in which poorlubrication of a bearing can be inhibited when an expander is driven.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing the configuration of a thermal energyrecovery device according to a first embodiment of the presentinvention.

FIG. 2 is a flow chart showing control details by a control unit.

FIG. 3 is a schematic view showing the configuration of a thermal energyrecovery device according to a second embodiment of the presentinvention.

FIG. 4 is a schematic view showing the configuration of a thermal energyrecovery device according to a third embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Modes for carrying out the present invention will hereinafter bedescribed in detail with reference to the accompanying drawings.

First Embodiment

FIG. 1 shows the configuration of a thermal energy recovery deviceaccording to a first embodiment of the present invention. The thermalenergy recovery device includes an evaporator 10, an expander 20, apower recovery machine 30, a condenser 40, a pump 50, a circulation flowpath 60 connecting the evaporator 10, the expander 20, the condenser 40,and the pump 50 in this order, a cooling flow path 70, and a controlunit 80.

The evaporator 10 evaporates working medium through heat exchangebetween the working medium and heating medium.

The expander 20 is provided at a site downstream the evaporator 10 inthe circulation flow path 60. The expander 20 expands working medium ofgas phase flowing out of the evaporator 10. In this embodiment, theexpander 20 employs a volumetric screw expander having a rotor to berotationally driven by the expansion energy of working medium of gasphase. Specifically, the expander 20 has a pair of male and female screwrotors (rotors) 21 to be rotationally driven by the expansion energy ofworking medium, bearings 22 that bear the screw rotors 21 such that thescrew rotors 21 are rotatable, and a primary casing 23 housing the pairof screw rotors 21 and the bearings 22 collectively. The primary casing23 has a suction port 23 a for sucking therethrough working mediumflowing out of the evaporator 10 and a discharge port 23 b fordischarging therethrough expanded working medium (after the pair ofscrew rotors 21 are rotationally driven) to the circulation flow path60. In this embodiment, the primary casing 23 is installed in a posturein which the discharge port 23 b is arranged horizontally. The bearings22 are held on the primary casing 23.

The power recovery machine 30 is connected to the expander 20.

Specifically, the power recovery machine 30 has a power recovery unit 31and a secondary casing 35.

The power recovery machine 30 is connected to one of the pair of screwrotors 21 to rotate together with the screw rotor 21 and thereby recoverpower. In this embodiment, the power recovery machine 30 employs agenerator. That is, the power recovery unit 31 has a rotating shaft 32connected to one of the pair of screw rotors 21, a rotor 33 fixed on therotating shaft 32, and a stator 34 arranged around the rotor 33. It isnoted that the power recovery machine 30 may employ a compressor or thelike.

The secondary casing 35 houses the power recovery unit 31 therein. Thesecondary casing 35 is fixed to the primary casing 23. The interior ofthe secondary casing 35 is in communication with the interior of theprimary casing 23. This allows working medium expanded within theprimary casing 23 to partially flow into the secondary casing 35.

The condenser 40 is provided at a site downstream the expander 20 in thecirculation flow path 60. The condenser 40 condenses working mediumflowing out of the expander 20 through heat exchange between the workingmedium and cooling medium (e.g. cooling water).

In this embodiment, a reservoir (receiver) 45 for reserving workingmedium of liquid phase is provided at a site downstream the condenser 40in the circulation flow path 60. It is noted, however, that thereservoir 45 may be formed by a part of the circulation flow path 60 ormay be omitted.

The pump 50 is provided at a site downstream the condenser 40 (betweenthe condenser 40 and the evaporator 10) in the circulation flow path 60.The pump 50 delivers working medium of liquid phase flowing out of thecondenser 40 to the evaporator 10 at a predetermined pressure.

The cooling flow path 70 supplies working medium of liquid phase flowingout of the pump 50 partially to the power recovery machine 30. In thisembodiment, the cooling flow path 70 connects a site of the circulationflow path 60 between the pump 50 and the evaporator 10 and the secondarycasing 35. Specifically, the secondary casing 35 has an introducingportion 35 a capable of introducing working medium of liquid phase intothe secondary casing 35, and a downstream end portion of the coolingflow path 70 is connected to the introducing portion 35 a. Accordingly,working medium of liquid phase discharged from the pump 50 is partiallysupplied into the secondary casing 35 through the cooling flow path 70.This allows the power recovery unit 31 to be cooled effectively.

The thermal energy recovery device of this embodiment further includes aliquid draining flow path 71. The liquid draining flow path 71 returnsthe working medium R of liquid phase within the primary casing 23 or thesecondary casing 35 to the downstream side of the expander 20 and theupstream side of the pump 50, that is, to a region in which workingmedium exists in liquid phase. Specifically, the liquid draining flowpath 71 connects a lead-out portion 23 c formed in the primary casing 23and a site of the circulation flow path 60 between the reservoir 45 andthe pump 50. The lead-out portion 23 c is provided in a bottom portion25 positioned lowermost in the primary casing 23. It is noted that adownstream end portion of the liquid draining flow path 71 may beconnected to a site of the circulation flow path 60 between the expander20 and the condenser 40, the interior of the condenser 40, or thereservoir 45.

The thermal energy recovery device of this embodiment further includes abypass flow path 62 for bypassing the expander 20, an on-off valve V1provided in the cooling flow path 70, a shutoff valve V2 provided in thecirculation flow path 60, a bypass valve V3 provided in the bypass flowpath 62, and a liquid draining valve V4 provided in the liquid drainingflow path 71. The valves V1 to V4 are arranged openable and closable.

An upstream end portion of the bypass flow path 62 is connected to asite of the circulation flow path 60 between the evaporator 10 and theexpander 20. A downstream end portion of the bypass flow path 62 isconnected to a site of the circulation flow path 60 between the expander20 and the condenser 40.

The shutoff valve V2 is provided at a site of the circulation flow path60 between a portion where the circulation flow path 60 and the upstreamend portion of the bypass flow path 62 are connected and the expander20.

During recovery of power (electric power in this embodiment) by thepower recovery machine 30 (when the expander 20, the power recoverymachine 30, and the pump 50 are driven), upon reception of a stop signalfor stopping the power recovery by the power recovery machine 30, thecontrol unit 80 stops cooling the power recovery unit 31, that is,supplying working medium of liquid phase discharged from the pump 50partially to the power recovery machine 30 through the cooling flow path70. Control details by the control unit 80 will hereinafter be describedwith reference to FIG. 2. It is noted that when the device is beingdriven, the on-off valve V1 and the shutoff valve V2 are opened, whilethe bypass valve V3 and the liquid draining valve V4 are closed.

Upon reception of the stop signal, the control unit 80 reduces therotational speed of the pump 50, the expander 20, and the power recoverymachine 30, closes the shutoff valve V2, and opens the bypass valve V3(step S11). This causes working medium of gas phase flowing out of theevaporator 10 to run through the bypass flow path 62 (bypass theexpander 20) to the condenser 40.

With the reduction in the rotational speed of the expander 20 and thepower recovery machine 30, the power recovery unit 31 is not required tobe cooled, and the control unit 80 therefore closes the on-off valve V1(step S12). As a result, the supply of working medium of liquid phasethrough the cooling flow path 70 into the secondary casing 35 isstopped. Accordingly, the power recovery unit 31 is inhibited from beingcooled excessively. In other words, accumulation of working medium R ofliquid phase within the secondary casing 35 and the primary casing 23 isinhibited.

After the pump 50 is stopped, the control unit 80 then opens the liquiddraining valve V4 (step S13). This causes the working medium R of liquidphase within the primary casing 23 or the secondary casing 35 isdischarged effectively from the casing 23 or 35.

As described heretofore, in the thermal energy recovery device, uponreception of the stop signal (when the power recovery unit 31 is notrequired to be cooled), the control unit 80 stops supplying workingmedium of liquid phase discharged from the pump 50 partially to thepower recovery machine 30 through the cooling flow path 70.Specifically, upon reception of the stop signal, the control unit 80closes the on-off valve V1 that is provided in the cooling flow path 70.This inhibits accumulation of working medium of liquid phase within thesecondary casing 35 and the primary casing 23. Accordingly, the bearings22 of the expander 20 is inhibited from being immersed in the workingmedium R of liquid phase and thereby poor lubrication of the bearings 22is inhibited when the thermal energy recovery device restarts.

In addition, since the control unit 80 opens the liquid draining valveV4 after the pump 50 is stopped in step S13, the working medium R ofliquid phase within the primary casing 23 or the secondary casing 35 isdischarged effectively from the casing 23 or 35 and, in additionthereto, the working medium is inhibited from flowing into the primarycasing 23 until the pump 50 is stopped. Specifically, if the liquiddraining valve V4 were opened before the pump 50 is stopped, the workingmedium discharged from the pump 50 to flow through the bypass flow path62 to the downstream side of the expander 20 might counterflow from thedownstream side of the expander 20 through the circulation flow path 60to flow into the primary casing 23 of the expander 20 to be liquefiedwithin the primary casing 23. In contrast, in this embodiment, since thecontrol unit 80 is arranged to open the liquid draining valve V4 afterthe pump 50 is stopped, such a trouble as described above is inhibited.

Second Embodiment

Next will be described a thermal energy recovery device according to asecond embodiment of the present invention with reference to FIG. 3. Itis noted that in the second embodiment, only components different fromthe first embodiment will be described, and the same structures,operations, and effects as in the first embodiment will not bedescribed.

In this embodiment, the power recovery machine 30 has a jacket 36, andthe downstream end portion of the cooling flow path 70 is connected tothe jacket 36.

The jacket 36 provided in the secondary casing 35 to form a coolingspace S that allows working medium of liquid phase to flow between thejacket 36 and the secondary casing 35. The jacket 36 is arranged on theoutside of the outer peripheral surface of the secondary casing 35. Thatis, the cooling space S is formed between the outer peripheral surfaceof the secondary casing 35 and the inner peripheral surface of thejacket 36. The jacket 36 has an introducing portion 36 a connectable tothe downstream end portion of the cooling flow path 70 and capable ofintroducing working medium of liquid phase supplied through the coolingflow path 70 into the cooling space S.

The cooling medium that has passed through the cooling space S to coolthe power recovery unit 31 via the secondary casing 35 also flows intothe circulation flow path 60 through a discharge flow path 72. Anupstream end portion of the discharge flow path 72 is connected to adischarge portion 36 b formed in the jacket 36, and a downstream endportion of the discharge flow path 72 is connected to a site of thecirculation flow path 60 between the expander 20 and the condenser 40.

As described heretofore, also in this embodiment, the bearings 22 of theexpander 20 is inhibited from being immersed in the working medium R ofliquid phase and thereby poor lubrication of the bearings 22 isinhibited when the thermal energy recovery device restarts.

Third Embodiment

Next will be described a thermal energy recovery device according to athird embodiment of the present invention with reference to FIG. 4. Itis noted that in the third embodiment, only components different fromthe first embodiment will be described, and the same structures,operations, and effects as in the first embodiment will not bedescribed.

While this embodiment shares similarity with the second embodiment inthat the power recovery machine 30 has a jacket 36, cooling medium (e.g.cooling water) different from the working medium is supplied to thecooling space S.

A cooling flow path 73 branched from a cooling medium supply line L1 forsupplying cooling medium therethrough is connected to the jacket 36.Accordingly, in this embodiment, cooling medium passing through thecooling space S cools the power recovery unit 31 via the secondarycasing 35. Cooling medium that has passed through the cooling space S isreturned through a cooling medium recovery flow path 74 connected to thejacket 36 to a cooling medium discharge line L2 for discharging coolingmedium therethrough.

As described heretofore, this embodiment also exhibits the same effectas the above-described embodiments.

It is noted that the above-disclosed embodiment should be construed asillustrative only and not restrictive in all aspects. The scope of thepresent invention is defined not by the above-described embodiment butby the appended claims and further includes all modifications within themeaning and scope equivalent to the appended claims.

For example, the secondary casing 35 and the jacket 36, which form thecooling space S, may be separate members or may be an integrally castedmember.

What is claimed is:
 1. A thermal energy recovery device comprising: anevaporator for evaporating working medium through heat exchange betweenheating medium and the working medium; an expander for expanding workingmedium flowing out of the evaporator; a power recovery machine connectedto the expander; a condenser for condensing working medium flowing outof the expander; a pump for delivering working medium flowing out of thecondenser to the evaporator; a circulation flow path connecting theevaporator, the expander, the condenser, and the pump in this order; acooling flow path for supplying working medium of liquid phase flowingout of the pump partially to the power recovery machine; an on-off valveprovided in the cooling flow path; and a control unit, wherein theexpander has: a rotor to be rotationally driven by the expansion energyof the working medium; a bearing that bears the rotor such that therotor is rotatable; and a primary casing housing the rotor and thebearing therein, and wherein the power recovery machine has: a powerrecovery unit connected to the rotor to rotate together with the rotorand thereby recover power; and a secondary casing housing the powerrecovery unit therein and having a shape in communication with theinterior of the primary casing, and wherein upon reception of a stopsignal for stopping power recovery by the power recovery machine, thecontrol unit closes the on-off valve.
 2. The thermal energy recoverydevice according to claim 1, wherein the secondary casing has anintroducing portion connectable to the cooling flow path and capable ofintroducing working medium of liquid phase supplied through the coolingflow path into the secondary casing.
 3. The thermal energy recoverydevice according to claim 1, wherein the power recovery machine furtherhas a jacket provided in the secondary casing to form a cooling spacethat allows working medium of liquid phase to flow between the jacketand the secondary casing, and wherein the jacket has an introducingportion connectable to the cooling flow path and capable of introducingworking medium of liquid phase supplied through the cooling flow pathinto the cooling space.
 4. A thermal energy recovery device comprising:an evaporator for evaporating working medium through heat exchangebetween heating medium and the working medium; an expander for expandingworking medium flowing out of the evaporator; a power recovery machineconnected to the expander; a condenser for condensing working mediumflowing out of the expander; a pump for delivering working mediumflowing out of the condenser to the evaporator; a circulation flow pathconnecting the evaporator, the expander, the condenser, and the pump inthis order; a cooling flow path for supplying cooling medium differentfrom the working medium to the power recovery machine to cool the powerrecovery machine; an on-off valve provided in the cooling flow path; anda control unit, wherein the expander has: a rotor to be rotationallydriven by the expansion energy of the working medium; a bearing thatbears the rotor such that the rotor is rotatable; and a primary casinghousing the rotor and the bearing therein, and wherein the powerrecovery machine has: a power recovery unit connected to the rotor torotate together with the rotor and thereby recover power; and asecondary casing housing the power recovery unit therein and having ashape in communication with the interior of the primary casing, andwherein upon reception of a stop signal for stopping power recovery bythe power recovery machine, the control unit closes the on-off valve. 5.The thermal energy recovery device according to claim 1, furthercomprising a liquid draining flow path for returning working medium ofliquid phase within the primary casing or the secondary casing to thedownstream side of the expander and the upstream side of the pump. 6.The thermal energy recovery device according to claim 5, furthercomprising: a liquid draining valve provided in the liquid draining flowpath; a bypass flow path for bypassing the expander; a bypass valveprovided in the bypass flow path; and a shutoff valve provided at a siteof the circulation flow path between a portion where the circulationflow path and an upstream end portion of the bypass flow path areconnected and the expander, wherein upon reception of a stop signal forstopping power recovery by the power recovery machine, the control unitreduces the rotational speed of the pump, closes the shutoff valve andopens the bypass valve, and closes the on-off valve and, after the pumpis stopped, opens the liquid draining valve.
 7. The thermal energyrecovery device according to claim 2, further comprising a liquiddraining flow path for returning working medium of liquid phase withinthe primary casing or the secondary casing to the downstream side of theexpander and the upstream side of the pump.
 8. The thermal energyrecovery device according to claim 3, further comprising a liquiddraining flow path for returning working medium of liquid phase withinthe primary casing or the secondary casing to the downstream side of theexpander and the upstream side of the pump.
 9. The thermal energyrecovery device according to claim 4, further comprising a liquiddraining flow path for returning working medium of liquid phase withinthe primary casing or the secondary casing to the downstream side of theexpander and the upstream side of the pump.